1. The Field of the Invention
The present invention relates to an apparatus and method for straightening bent steel sheet piles. While found to be particularly useful in straightening piles having a "Z" cross section, the present invention is applicable to sheet piles of almost any cross section.
2. Description of the Prior Art
Steel sheet piles are hot-rolled metal sections used for shoring up ditches or other excavations while work, such as laying pipe, is being done within the ditch or excavation. When the work is completed, the piles are removed so that they can be used on a different part of the same project or on a subsequent project.
Because these piles are driven vertically into the ground by a pile driver, the piles have a tendency to flatten out at the lower end and bend along a substantial portion of the lower length of the pile. Such flattening out or bending renders the pile essentially worthless for any subsequent use unless the distorted portion is corrected.
Under present practice, the bent piles are repaired by severing the flattened or bent end and replacing it with a good piece cut from a second pile. The good piece is usually attached by welding it to the first pile. The severed piece is then sold as scrap. See U.S. Pat. No. 3,720,068 issued Mar. 13, 1973, to E. R. DeRosa and U.S. Pat. No. 3,796,057 issued Mar. 12, 1974, to J. J. Dougherty for pile splicing techniques.
Pile splicing, however, is inefficient since it often requires several feet of a standard pile to be scrapped after a single use of the pile. This loss can be a significant expense during a major job. Such a loss is eliminated if, instead of scrapping the bent portion of the sheet pile, the sheet pile is reformed to its original shape.
The process of shaping metal by vising a piece of metal between dies is known. See, for example: U.S. Pat. No. 3,753,368 issued Aug. 21, 1973, to Lang; U.S. Pat. No. 3,119,432 issued Jan. 28, 1964, to Rogers; U.S. Pat. No. 3,610,019 issued Oct. 5, 1971, to Denninger; and U.S. Pat. No. 2,579,030 issued Dec. 18, 1951, to Brauchler. Lang, Rogers and Brauchler teach forcing a movable die against a stationary die upon which the piece to be formed is resting. Lang, for example, shows the use of such dies for reforming bent bumpers to their original shape by forcing a movable die against a stationary die with a "pressing machine."
The prior art, however, teaches a movable die activated by a force applicator moving in only one direction. Because a sheet pile is commonly bent in several planes, some of which may be perpendicular to one another, a force applicator moving in only one direction is insufficient. Furthermore, the molds and dies taught by the prior art are susceptible only to use of a force applicator moving in a single direction. Also the technique shown by Lang requires placing the bent piece over or in the cavity of the female die member. (See FIG. 6 of the Drawings in Lang). It is possible for a pile to be bent so badly when driven into the ground that it could not fit over such a cavity without some initial bending.